From 2e9433d42da2a7bc756b7c1cb4a654dc906a7e7e Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Sat, 16 Jul 2016 18:29:26 +0000
Subject: [PATCH] [InstCombine] allow X + signbit --> X ^ signbit for vector
splats
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275691 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/InstCombine/InstCombineAddSub.cpp | 13 ++++++++++---
test/Transforms/InstCombine/apint-add.ll | 2 +-
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index f94a65a75f0..221a2200717 100644
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1042,12 +1042,16 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Value *V = SimplifyUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
- if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
+ const APInt *Val;
+ if (match(RHS, m_APInt(Val))) {
// X + (signbit) --> X ^ signbit
- const APInt &Val = CI->getValue();
- if (Val.isSignBit())
+ if (Val->isSignBit())
return BinaryOperator::CreateXor(LHS, RHS);
+ }
+ // FIXME: Use the match above instead of dyn_cast to allow these transforms
+ // for splat vectors.
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
// See if SimplifyDemandedBits can simplify this. This handles stuff like
// (X & 254)+1 -> (X&254)|1
if (SimplifyDemandedInstructionBits(I))
@@ -1149,6 +1153,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
return BinaryOperator::CreateSub(SubOne(CRHS), X);
}
+ // FIXME: We already did a check for ConstantInt RHS above this.
+ // FIXME: Is this pattern covered by another fold? No regression tests fail on
+ // removal.
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
// (X & FF00) + xx00 -> (X+xx00) & FF00
Value *X;
diff --git a/test/Transforms/InstCombine/apint-add.ll b/test/Transforms/InstCombine/apint-add.ll
index f27af7b60cc..6740ae66aef 100644
--- a/test/Transforms/InstCombine/apint-add.ll
+++ b/test/Transforms/InstCombine/apint-add.ll
@@ -36,7 +36,7 @@ define i15 @test3(i15 %x) {
; X + signbit --> X ^ signbit
define <2 x i5> @test3vec(<2 x i5> %x) {
; CHECK-LABEL: @test3vec(
-; CHECK-NEXT: [[Y:%.*]] = add <2 x i5> %x, <i5 -16, i5 -16>
+; CHECK-NEXT: [[Y:%.*]] = xor <2 x i5> %x, <i5 -16, i5 -16>
; CHECK-NEXT: ret <2 x i5> [[Y]]
;
%y = add <2 x i5> %x, <i5 16, i5 16>
--
2.40.0